Thalamic structures involved in the unpleasant emotional or affective aspect of pain are poorly understood. We now describe studies of the region of the thalamic principal somatosensory nucleus (Vc) performed before thalamotomy for tremor in a patient who also had panic disorder. Microstimulation in the region posterior to Vc evoked chest pain, including a strong affective dimension, almost identical to that occurring during his panic attacks, as measured using a questionnaire. Results in our other patients indicate that stimulation-associated pain with a strong affective dimension occurred only in those patients who had previously experienced spontaneous pain with a strong affective component. These results are consistent with stimulation-evoked activation of limbic structures, which are connected through cortex with the region posterior to Vc and involved in the affective dimension of pain through conditioning by previous experience.